[lit] When setting SDKROOT on Darwin, use '--sdk macosx' to find the right SDK path.

This will make sure that we find an actual path in case you have Command Line Tools installed.

llvm-svn: 287403

llvm/utils/lit/lit/util.py

@@ -251,7 +251,7 @@ def usePlatformSdkOnDarwin(config, lit_config):
     # default system root path.
     if 'darwin' in config.target_triple:
         try:
-            cmd = subprocess.Popen(['xcrun', '--show-sdk-path'],
+            cmd = subprocess.Popen(['xcrun', '--show-sdk-path', '--sdk', 'macosx'],
                                    stdout=subprocess.PIPE, stderr=subprocess.PIPE)
             out, err = cmd.communicate()
             out = out.strip()